Sunlight concentrating and harvesting device

ABSTRACT

Device for concentrating and harvesting sunlight comprising: A panel having rigid layer having a patterned electrical circuit thereon. An array of sunlight concentrating and harvesting units, each unit being formed by at least one rigid element and a portion of the rigid layer; and including: a rigid optical concentrating element, a photovoltaic cell sandwiched within the panel for converting sunlight into electrical energy, and an electrical conductor. The electrical conductor being the primary heat sink for the photovoltaic cell, the photovoltaic cell being primarily cooled via conduction. The electrical conductor and the optical concentrating element being dimensioned and arranged within the unit such that the electrical conductor does not materially impede transmission of sunlight to the photovoltaic cell. The electrical conductor transmitting electrical and thermal energy received from the photovoltaic cell away from the unit.

CROSS-REFERENCE

The present application claims priority to U.S. Provisional PatentApplication No. 61/798,205, filed Mar. 15, 2013, entitled “ConcentratedPhotovoltaic Panel” the entirety of which is incorporated herein byreference for all purposes. The present application also claims priorityto or the benefit of the following applications filed on Mar. 4, 2014:U.S. patent application Ser. Nos. 14/196,523; 14/196,291 and 14/196,618;U.S. Provisional Patent Application No. 61/948,020; and InternationalPatent Application Nos. PCT/CA2014/050168 and PCT/CA2014/000167. Thepresent application also claims the benefit of the following applicationfiled on Mar. 17, 2014: U.S. patent application Ser. No. 14/215,913.

FIELD

The present technology relates to devices for concentrating andharvesting sunlight.

BACKGROUND

One way to harvest solar energy is to use concentrated solar powersystems such as concentrated photovoltaic systems that employ opticalcomponents to concentrate solar energy (sometimes to great degrees) ontophotovoltaic cells. Compact optical systems and components forconcentrating solar energy have been developed over the years. Some ofthese designs comprise a two-stage solar concentrator or collector inwhich a light focusing layer is optically coupled to a light redirectinglayer. The redirecting layer includes a light-guide that guides thesunlight laterally within the light-guide towards a solar collector bytotal internal reflections with almost no loss of energy. Severalexamples are shown in United States Patent Application Publication No.2012/0019942, entitled “Light-Guide Solar Panel and Method ofFabrication Thereof” which is assigned to the applicant of the presentapplication.

One of the difficulties with concentrated photovoltaic systems is that arelatively significant amount of heat (thermal energy) is generated atthe photovoltaic cell, which can reduce the efficiency oflight-to-electricity conversion by the cell, and should be removed fromthe cell during operation of the device. In order to transfer this heataway from the cell, conventional concentrated photovoltaic systemstypically have the photovoltaic cell on an outer surface of the device,attached a large heat sink. While such designs are adequate for theirintended purpose, improvements in this area may nonetheless bedesirable.

SUMMARY

It is an object of the present technology to ameliorate at least one ofthe inconveniences present in conventional concentrated photovoltaicsystems, be it one of the inconveniences described above or otherwise.

In one aspect, embodiments of the present technology provide a devicefor concentrating and harvesting sunlight comprising:

a panel having at least one rigid layer, the at least one rigid layerhaving at least one patterned electrical circuit thereon;

an array of sunlight concentrating and harvesting units, each unit beingformed by at least one rigid element and a portion of the at least onerigid layer, each unit including:

-   -   a rigid optical concentrating element secured to the at least        one rigid layer for concentrating sunlight received by the unit,    -   a photovoltaic cell secured to the at least one rigid layer and        sandwiched within the panel for converting concentrated sunlight        into electrical energy, and    -   an electrical conductor in electrical communication with the        photovoltaic cell to receive electrical energy therefrom, the        electrical conductor being in thermal communication with the        photovoltaic cell to receive thermal energy therefrom, the        electrical conductor being the primary heat sink for the        photovoltaic cell, the photovoltaic cell being primarily cooled        via conduction;    -   the electrical conductor and the optical concentrating element        of each unit being dimensioned and arranged within the unit such        that the electrical conductor does not materially impede        transmission of sunlight received by the unit within the unit to        the photovoltaic cell;    -   the electrical conductor being at least electrically and        thermally interconnected with the patterned circuit to transmit        electrical energy and thermal energy received from the        photovoltaic cell away from the unit.

In the context of the present specification, the term “rigid” should beunderstood to mean that a “rigid” structure is one that generallymaintains its form under normal operating conditions on its own, withoutrequiring external forces (such as those generated by a pressured gas)to do so. “Rigid”, however, in the present context does not mean thatthe structure in question is completely inflexible; as structures whichare slightly flexible or expandable and return to their original sizeand shape after flexion (and/or expansion) are included within thedefinition of “rigid” in the present context.

In the context of the present specification a “patterned” electricalcircuit should be understood to be an electric circuit not of a randomlayout. In some embodiments, the patterned electrical circuit includesportions that are of a repeating design.

In the context of the present specification two elements may be“secured” together in any number of various ways. For example, suchelements may bonded to one another (be it permanently or releasably), bybeing formed together in a single physical element, by being held inplace one with respect to another by other elements, etc.

In the context of the present specification, an electrical conductor isconsidered to be the primary heat sink for the photovoltaic cell whenunder normal operating conditions of the device, a greater amount ofthermal energy transferred away from the photovoltaic cell via directconduction is transferred away via the electrical conductor than via anyother element of the device.

In the context of the present specification, a photovoltaic cell isconsidered to be primarily cooled via conduction when under normaloperating conditions of the device, more thermal energy is transferredaway from the photovoltaic cell via direct conduction than via directconvection or direct radiation.

In the context of the present specification, two elements areelectrically interconnected when electricity can pass between them, beit directly or indirectly. Thus, two elements may, for example, beelectrically interconnected via their direct physical connection to eachother or via their direct physical connection to a third element, etc.

In the context of the present specification, two elements are thermallyinterconnected when thermal energy can transfer between them viaconduction, either directly, or indirectly through a third element.

In some embodiments the photovoltaic cell is sandwiched between the atleast one rigid layer and the rigid optical concentrating element.

In some embodiments the optical concentrating element of each unit is aseries of optical concentrating elements. In some such embodiments theoptical concentrating element of each unit is a series of concentricannular optical concentrating elements.

In some embodiments the rigid optical concentrating elements of multipleunits are all part of a single rigid layer distinct from the at leastone rigid layer having the at least one patterned electrical circuitthereon.

In some embodiments the electrical conductor and the opticalconcentrating element of each unit being dimensioned and arranged withinthe unit such that the electrical conductor impedes transmission of nomore than 20% of sunlight received by the unit within the unit to thephotovoltaic cell.

In some embodiments, each unit of the array further includes a rigidoptical redirecting element secured to the at least one rigid layer forredirecting sunlight received by the unit; and the electrical conductor,the optical concentrating element, and the optical redirecting elementof each unit are dimensioned and arranged within the unit such that theelectrical conductor does not materially impede transmission of sunlightreceived by the unit within the unit to the photovoltaic cell.

In some embodiments the photovoltaic cell is sandwiched between the atleast one rigid layer and the rigid optical concentrating element.

In some embodiments the photovoltaic cell is sandwiched between the atleast one rigid layer and the rigid optical redirecting element.

In some embodiments the optical redirecting element of each unit is aseries of optical redirecting elements.

In some embodiments, the optical concentrating element of each unit is aseries of optical concentrating elements; and the optical redirectingelement of each unit is a series of optical redirecting elements.

In some embodiments, the optical concentrating element of each unit is aseries of concentric annular optical concentrating elements; and theoptical redirecting element of each unit is a series of concentricannular optical redirecting elements.

In some embodiments, the rigid optical concentrating elements ofmultiple units are all part of a first single rigid layer distinct fromthe at least one rigid layer having the at least one patternedelectrical circuit thereon; and the rigid optical redirecting elementsof multiple units are all part of a second single rigid layer distinctfrom the at least one rigid layer having the at least one patternedelectrical circuit thereon and the first single rigid layer.

In some embodiments, the rigid optical redirecting element redirectslight into a light guide for transmission to the photovoltaic cell.

In some embodiments the light guide has a secondary optical element forredirecting light in the light guide.

In some embodiments, the electrical conductor, the optical concentratingelement, and the optical redirecting element of each unit aredimensioned and arranged within the unit such that the electricalconductor impedes transmission of not more than 20% of sunlight receivedby the unit within the unit to the photovoltaic cell.

In some embodiments the photovoltaic cell is at least partially encasedin a thermal insulator.

In some embodiments, the electrical conductor is a part of the patternedcircuit. In other embodiments, the electrical conductor is a distinctelement from the patterned circuit.

In another aspect, embodiments of the present technology provide adevice for concentrating and harvesting sunlight comprising:

a panel having a plurality of rigid layers bonded together;

an array of sunlight concentrating and harvesting units formed by theplurality of layers of the panel, each one of the array of sunlightconcentrating and harvesting units including:

-   -   a series of optical concentrating elements associated with a        first surface of one of the layers of the plurality of layers        for concentrating sunlight received by the unit;    -   a series of optical redirecting elements associated with a        second surface of one of the layers of the plurality of layers        for redirecting sunlight received by the unit;    -   a photovoltaic cell sandwiched between two of the layers of the        plurality of layers for converting concentrated and redirected        sunlight into electrical energy;    -   one of the layers of the plurality of layers having an        electrical conductor in electrical communication with the        photovoltaic cell to receive electrical energy therefrom, the        electrical conductor being in thermal communication with the        photovoltaic cell to receive thermal energy therefrom, the        electrical conductor being the primary heat sink for the        photovoltaic cell, the photovoltaic cell being primarily cooled        via conduction;    -   the electrical conductor, the series of optical concentrating        elements and the series of optical redirecting elements being        dimensioned and arranged within the unit such that the        electrical conductor does not materially impede transmission of        sunlight received by the unit within the unit to the        photovoltaic cell;    -   one of the layers of the plurality of layers having a patterned        circuit electrically and thermally interconnected with        photovoltaic cells of at least some of the units to receive        electrical energy and thermal energy therefrom for transmission        away from the units.

In some embodiments, the series of optical concentrating elements areformed on the first surface; and the series of optical redirectingelements are formed on the second surface.

In some embodiments, the electrical conductor, the optical concentratingelement, and the optical redirecting element of each unit aredimensioned and arranged within the unit such that the electricalconductor impedes transmission of not more than 20% of sunlight receivedby the unit within the unit to the photovoltaic cell.

Embodiments of the present technology each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presenttechnology that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects and advantages ofembodiments of the present technology will become apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a perspective view of a conventional (prior art) photovoltaicpanel;

FIG. 2 is a rear perspective view of an embodiment of a concentratedphotovoltaic panel including the present technology;

FIG. 3 is an exploded perspective view of the concentrated photovoltaicpanel apparatus of the concentrated photovoltaic panel of FIG. 2;

FIG. 4 is a plan view of an embodiment of a receiver substrate assembly;

FIG. 5 is a detail view of a portion of the receiver substrate assemblyof FIG. 4;

FIG. 6 is a rear plan view of an alternate embodiment of a receiversubstrate assembly having two arrays of receiver assemblies;

FIG. 7A is a perspective view of an embodiment of a heat spreaderportion of a receiver substrate assembly;

FIG. 7B is a perspective view of another embodiment of a heat spreaderportion of a receiver substrate assembly;

FIG. 8A is a perspective view of another embodiment of a heat spreaderportion of a receiver substrate assembly;

FIG. 8 b is a perspective view of a cell receiver assembly including theheat spreader portion of FIG. 8A;

FIG. 8C is an exploded view of an embodiment of an optical unitincluding the heat spreader portion of FIG. 8A;

FIG. 9 is a cross-sectional view of an embodiment of an optical unitthat has a curved light guide optic;

FIG. 10 is a cross-sectional view of an embodiment of an optical unitthat has a focusing optic and a light guide optic, and the focusingoptic reflects light directly to a conditioning surface;

FIG. 11 a cross-sectional view of an embodiment of an optical unit inwhich the light guide optic has reflecting surfaces that reflect lightin three different paths;

FIG. 12 a cross-sectional view of another embodiment of an optical unitin which the light guide optic has reflecting surfaces that reflectlight in three different paths;

FIG. 13 is a cross-sectional view of an embodiment of an optical unitwhere the light guide optic includes tertiary reflectors;

FIG. 14 is a cross-sectional view of another embodiment of an opticalunit where the light guide optic includes tertiary reflectors;

FIG. 15 is a cross-sectional view of an embodiment of an optical unitthat has a redirecting optic between the receiver substrate assembly andthe light guide optic;

FIG. 16 is a cross-sectional view of another embodiment of an opticalunit in which the light guide optic has tertiary reflectors;

FIG. 17 is a cross-sectional view of an embodiment of an optical unit inwhich the light guide optic includes lenses;

FIG. 18 is a cross-sectional view of an embodiment of an optical unitthat has the receiver assembly on the second surface or the rigid sheet;

FIG. 19 is a cross-sectional view of another embodiment of an opticalunit that has the receiver assembly on the second surface or the rigidsheet;

FIG. 20 is a cross-sectional view of another embodiment of an opticalunit that has a redirecting optic between the receiver substrateassembly and the light guide optic;

FIG. 21 is a cross-sectional view of an embodiment of an optical unit inwhich the light guide optic has focussing portions and guiding portions;

FIG. 22 is a cross-sectional view of an embodiment of an optical unit inwhich the light guide has three stages;

FIG. 23 is a cross-sectional view of an embodiment of an optical unit inwhich the focusing optic has lenses and redirecting surfaces;

FIGS. 24A and 24B show cross-sectional views of an embodiment of anoptical unit transmitting light through the gaps in a heat spreaderportion, and where the light guide optic has a redirecting portion and aguiding portion;

FIG. 24C is an exploded view of the light guide optic and envelope ofFIGS. 24A and 24B

FIG. 25 is a cross-sectional view of another embodiment of an opticalunit transmitting light through the gaps in a heat spreader portion, andwhere the light guide optic has a redirecting portion and a guidingportion;

FIG. 26 is a cross-sectional view of another embodiment of an opticalunit transmitting light through the gaps in a heat spreader portion, andwhere the light guide optic has a redirecting portion and a guidingportion; and

FIG. 27 is a perspective view of another embodiment of an optical unit.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

FIG. 2 is a rear perspective view of an embodiment of a concentratedphotovoltaic (CPV) panel 2 (a device for concentrating and harvestingsunlight) of the present technology. In this embodiment, the CPV panel 2has a receiver substrate assembly 10, light-guide optics 40 attached tothe receiver substrate assembly 10, focusing optics 50 (shown in FIG. 3)attached to the receiver substrate assembly 10 (collectively referred toherein as “CPV panel apparatus” 6), a panel frame 4 and a junction box38. (In other embodiments, the structure of a CPV panel may different.For example, in other embodiments the focusing optics 50 may not bepresent.) In this embodiment, the CPV panel 2 is made to have dimensionssimilar to those of a conventional non-concentrating photovoltaic panel100, such as that shown in FIG. 1, and thereby serve as a replacementproduct in suitable deployments (e.g., may replace conventionalphotovoltaic panels mounted on a tracker). This is not required to bethe case, and in other embodiments, CPV panels may be of differentdimensions.

In this embodiment, the receiver substrate assembly 10 includes a rigidsheet 12 of light transmissive material with a conductor pattern 30(including a patterned electrical circuit) and receiver assemblies 20affixed thereto. The rigid sheet 12 has a first surface 14 and a secondsurface 16 opposite the first surface 14. Each receiver assembly 20 isattached to the first surface 14 of the rigid sheet 12 and electricallyconnected to the conductor pattern 30. For example, each receiverassembly 20 can be bonded to the rigid sheet 12 at bond sites 26 with aconductive epoxy, which can allow attachment to the rigid sheet 12 andelectrical connection to the conductor pattern 30 in a single stepduring assembly. Alternatively, positive and negative contacts of eachreceiver assembly 20 may be soldered to the conductor pattern 30. In yetother embodiments, one of the positive or negative contacts of eachreceiver assembly 20 may be soldered to or bonded with a conductiveepoxy to the conductor pattern 30 while the other contact iselectrically connected to the conductor pattern 30 by wire bonding,spring clipping or any other means known in the art.

The conductor pattern 30 provides electrical paths between the receiverassemblies 20 and the junction box 38. In the embodiment illustrated inFIGS. 3, 4 & 5, the conductor pattern 30 includes a positive bus bar 34,a negative bus bar 36 and a plurality of interconnection traces 32 whichconnect, directly or indirectly, each receiver assembly 20 to the busbars 34, 36. In the embodiment of FIG. 4, the conductor pattern 30electrically connects 22 strings of 16 series-connected receiverassemblies 20 in parallel. In other embodiments, the conductor pattern30 can be designed to provide electrical paths for two or more arrays 60of receiver assemblies 20. As shown in FIG. 6, the conductor pattern 30can comprise two halves 30 a, 30 b, each of which provide electricalpaths for an array 60 of receiver assemblies 20 to a junction box 38. Aswill be appreciated by a person skilled in the art, patterns other thanthose shown and/or described herein may be used to suit specificapplications.

The conductor pattern 30 is formed of an electrically conductive metalsuch as silver or copper. The conductor pattern 30 can be applied ontothe first surface 14 of the rigid sheet 12 by any suitable metalizationprocess, which could, for example, include sputtering, galvanizing orscreen printing a thick film. Alternatively, conductors, such as wires,ribbons and/or foils, can be attached to the rigid sheet 12 using abonding agent such as epoxy and/or by soldering the conductors tometalizations on the rigid sheet 12 (e.g., metalized dots).

Unlike conventional solar concentrators, the conductor pattern 30 issandwiched within the panel 2 (for example, in some embodiments, betweenthe rigid sheet 12 and either a light guide optic 40 or a focusing optic50).

The conductor pattern 30 may also serve as a heat spreader by spreadingthe heat generated at the photovoltaic cell 24 away from thephotovoltaic cell 24 via conduction, to be dissipated through the rigidsheet 12 and the light guide optic 40. Where the optical units 8(comprising the light guide optic 40, the photovoltaic cell 24 and,where present, the focusing optic 50) are sufficiently small, theinterconnection traces 32 of the conductor pattern 30 may be capable ofdissipating heat from the photovoltaic cell 24 fast enough to keep thephotovoltaic cell 24 cool enough to operate efficiently. However, forlarger optical units 8, the interconnection traces 32 may beinsufficient for cooling the photovoltaic cell 24. More elaborateconductor patterns 30 that have heat spreader portions 70 electricallyand thermally connected to the interconnection traces 32 may thereforebe employed to cool larger optical units 8. The larger the optical unit8, the greater the surface area of the conductor pattern 30 required.

FIGS. 7A & 7B show substantially flat heat spreader portions 70 a, 70 bof conductor pattern 30. The heat spreader portion 70 a has a positivehalf and a negative half. The positive half includes a positive terminus72, positive arms 76 and interconnection traces 32 electrically andthermally connecting the positive terminus 72 and the positive arms 76.The negative half includes a negative terminus 74, negative arms 78 andinterconnection traces 32 electrically and thermally connecting thenegative terminus 74 and the negative arms 78. The positive terminus 72is disposed proximate to the negative terminus 74 to allow theirconnection (e.g., by soldering) with the positive and negative contactsof the receiver assembly 20. The interconnection traces 32 extendingfrom the heat spreader portion 70 a electrically connect the positivehalf of one heat spreader portion 70 a to the negative half of the nextheat spreader trace 70 a of the string or a bus bar 34, 36. Gaps 80 areprovided between arms 76, 78 to facilitate heat dissipation and to allowlight to be focused therethrough by the focusing optic 50 into the lightguide optic 40. The heat spreader portion 70 a is designed to allowlight to be transmitted from the focusing optic 50 to the light guideoptic 40 with little shading. The heat spreader portion 70 a illustratedin FIG. 7A allows light from concentric lenses (e.g., toroidal lenses)of a focusing optic 50 to pass through gaps 80, through the rigid sheet12 and into the light guide optic 40, shaded only by the interconnectiontraces 32. The heat spreader portion 70 b can be scaled to accommodatelarger optical units 8 by increasing the number of positive and negativearms 76, 78, as shown in FIG. 7B. Such heat spreader portions 70 a, 70 bcan be metalized onto the rigid sheet 12 or stamped from a sheet or foilof conductive material (commonly used in the fabrication of circuitboards) such as conductive metals (e.g., copper, gold or aluminum) andpolymers loaded with conductive materials and bonded to the rigid sheet12.

In another embodiment, the heat spreader portion 70 may have one or morefins 82, 84 extending outwardly from the first surface 14 of the rigidsheet 12. FIGS. 8A-8C show a heat spreader portion 90 a, 90 b that haspositive arms 76, negative arms 78, a positive terminus 72 and anegative terminus 74, all of which lie flat against the rigid sheet.These portions the lie flat against the rigid sheet 12 can be metalizedonto the rigid sheet 12 or can be attached to the rigid sheet 12 with anadhesive or soldered to metalizations on the rigid sheet 12. The heatspreader portion further has a positive fin 82 and a negative fin 84,which, in the illustrated embodiment, are attached to and extendperpendicularly from those portions that lie flat against the rigidsheet 12.

The heat spreader portion 90 a shown in FIG. 8A can be stamped for asingle sheet of conductive material and bent or folded to form thefunctional heat spreader portion 90 a. Alternatively, each of thepositive half and the negative half of the heat spreader portion 90 acan be integrally formed, for example, by 3D printing onto the rigidsheet 12 or molding each half of the heat spreader portion 90 a andattaching it to the rigid sheet 12 with an adhesive or by soldering tometalizations on the rigid sheet 12.

In the embodiment of FIG. 8B, the positive arms 76 and negative arms 78of the heat spreader portion 90 b are more densely packed therebyincreasing the surface area over which heat can be dissipated. FIG. 8Balso illustrates how the positive arms 76, negative arms 78, positiveterminus 72 and negative terminus 74 lie flat against the rigid sheet 12and the positive fin 82 and negative fin 84 extend perpendicularly fromthose portions that lie flat against the rigid sheet 12. This heatspreader portion 90 b cannot be stamped from a single sheet ofconductive material. Instead the parts that lie flat against the rigidsheet 12 can be metalized onto the rigid sheet 12 or stamped from asheet of conductive material or otherwise formed and bonded to the rigidsheet 12, while the positive and negative fins 82, 84 must be separatelystamped from a sheet of conductive material or otherwise formed and besoldered or attached to those portions that lie flat against the rigidsheet 12 with an electrically and thermally conductive adhesive.Alternatively, each of the positive half and the negative half of theheat spreader portion 90 b can be integrally formed, for example, by 3Dprinting onto the rigid sheet 12 or molding each half of the heatspreader portion 90 b and attaching it to the rigid sheet 12. As shownin FIG. 8B the receiver assembly 20 can be mounted across the positiveterminus 72 and the negative terminus 74 for connection with thepositive terminus 72 and the negative terminus 74. The positive fin 82and the negative fin 84 can have bent portions 82 p, 84 n to accommodatethe receiver assembly 20. The bent portions 82 p, 82 n should have aheight from the rigid sheet that is short enough not to impede thetransmission of light from the light guide optic 40 to the photovoltaiccell 24. The positive fin 82 electrically and thermally interconnect thepositive arms 76 and the positive terminus 72. Similarly, the negativefin 84 electrically and thermally interconnect the negative arms 78 andthe negative terminus 74. As shown in FIG. 8C, the light guide optic 40can be provided with a groove 86 to accommodate the fins 82, 84. Use ofsuch fins 82, 84 may reduce shading while increasing the surface areafor dissipation of heat, and facilitate alignment of the light guideoptic 40 with the receiver assembly 20 and thereby the photovoltaic cell24.

The conductor pattern 30 can additionally or alternatively serve asand/or include alignment markers to facilitate assembly of the CPV panelapparatus 6. Alignment markers could, for example, be metalized dots(not shown). Alignment markers could, for example, facilitate thelocation of bond sites 26 for dispensing of a bonding agent forattachment of the receiver assemblies 20 to the rigid sheet 12 andplacement of the receiver assemblies 20 on the rigid sheet 12. Alignmentmarkers could also facilitate alignment of the light-guide optic 40 andthe receiver assembly 20 (more particularly, the photovoltaic cell 24)of each optical unit 8. Where the optical unit 8 includes a focusingoptic 50 for insertion of light into the light-guide optic 40 to beguided thereby toward the photovoltaic cell 24, alignment markers couldfacilitate alignment of the focusing optic 50 with the light guide optic40.

Each receiver assembly 20 includes a photovoltaic cell 24 for conversionof concentrated sunlight into electricity. Each photovoltaic cell 24 canbe mounted on a receiver substrate 22 of the receiver assembly 20 and isin electrical communication with the conductor pattern 30.

The photovoltaic cell 24 can be a high efficiency photovoltaic cell,such as a multi-junction solar cell. For example, the photovoltaic cell24 can be a GaInP/GaInAs/Ge III-V triple-junction solar cell.

The receiver assembly 20 can also include a bypass diode (not shown) toprevent the failure of a string of receiver assemblies 20 connected inseries due to failure, shading or any other issues that would cause oneof the series connected receiver assemblies 20 to enter an open circuitstate. Alternatively, the bypass diode may be separate from the receiverassembly 20 and may be electrically connected directly to theinterconnection traces 32 (e.g., by soldering the bypass diode to eachend of a discontinuity in the interconnection traces).

The receiver substrate 22 provides a medium on which electricalconnections can be made between the electrical components of thereceiver assembly 20, including the photovoltaic cell 24 and, ifpresent, the bypass diode, and the conductor pattern 30. Electricalcomponents of the receiver assembly 20 may be soldered to conductors onthe receiver substrate 22 to form electrical connections. The receiversubstrate 22 can be a surface mount substrate with positive and negativecontacts on the backside of the substrate (i.e., the surface of thesubstrate opposite that on which the photovoltaic cell 24 is mounted)for electrical connection to the conductor pattern 30.

The light guide optics 40 are made of a light transmissive material andguide light received via the rigid sheet 12 substantially laterallytoward their associated photovoltaic cells 24. Each light guide optic 40has a central axis and rotational symmetry about the central axis 44.Light is guided by the light-guide optics 40 by at least one reflectionon at least one reflective surface 42. The at least one reflection onthe at least one reflective surface 42 can be total internal reflectionson surfaces that interface with materials having a lower index ofrefraction than the light-guide optics 40, reflections on mirror coatedsurfaces of the light-guide optics 40 or a combination thereof. The oneor more reflective surfaces 42 can form concentric rings about thecentral axis 44, an example of which is shown in FIG. 3.

Each focusing optic 50 is made of a light transmissive material anddirects light towards one or more reflective surfaces 42 of anassociated light-guide optic 40. Use of focusing optics 50 may thereforeallow for thinner CPV panel apparatus 6 than would otherwise bepossible.

Non-limiting examples of light transmissive materials that may be usedto form the rigid sheet 12, the light guide optics 40 and/or thefocusing optics 50 include glass, light transmissive polymeric materialssuch as rigid, injection molded poly(methyl methacrylate) (PMMA),polymethyl methacrylimide (PMMI), polycarbonates, cyclo olefin polymers(COP), cyclo olefin copolymers (COC), polytetrafluoroethylene (PTFE), ora combination of these materials. For example, the rigid sheet 12 can bea sheet of glass, and the light guide optics 40 and the focusing optics50 can be made of PMMA. Alternatively, the light guide optics 40 and/orthe focusing optics 50 can be made of a silicone rubber such as siliconehaving hardness, when cured, of at least 20 Shore A. Attachment of eachlight-guide optic 40 and focusing optic 50 to the receiver substrateassembly 10 can be achieved by optically bonding the optics 40, 50 tothe receiver substrate assembly 10 with an optical bonding agent, laserwelding (where the rigid sheet 12 and the light-guide optics 40 andfocusing optics are made of polymers) or any other means known in theart. As an example, if the light guide optics 40 and the focusing optics50 are made of a polymeric material, they can be optically bonded to theglass rigid sheet 12 using an optical adhesive such as a silicone.Alternatively, the light guide optics 40 and the focusing optics 50 canbe 3D printed directly on the glass rigid sheet 12 or the surfaces ofthe receiver substrate assembly 10 can be coated with a polymer, such asa silicone rubber, and the polymeric light guide optics 40 and focusingoptics 50 can be 3D printed thereon.

Although FIGS. 2 and 3 show circular light guide optics 40 and circularfocusing optics 50, the light guide optics 40 and/or the focusing optics50 can be cropped into a tileable shape such as a square or a hexagon toeliminate dead space between optical units 8.

FIG. 9 is a cross sectional view of an optical unit 108 having aparabolic light guide optic 140 optically bonded to the first surface 14of a receiver substrate assembly 10. In this embodiment, light 11,typically from the sun, impinges on the rigid sheet 12 at an anglesubstantially normal to the second surface 16. The light 11 istransmitted through the rigid sheet 12, exiting through the firstsurface 14 into the light guide optic 140. The reflective surface 142can be parabolic in shape and have a mirror coating 148 to reflect thelight impinging thereon towards the focus of the parabola where aphotovoltaic cell 24 can be placed to convert the light 11 intoelectricity. Non-limiting examples of materials that can be used for themirror coating 148 are metals such as aluminum or silver, or adielectric.

In some embodiments a cell envelope 21 may surround the photovoltaiccell 24, which is typically the hottest portion of an optical unit 108,and serve as thermal insulation to protect the physical integrity of thematerials of the light guide optic 40. Where the receiver assembly 20 isattached to a rigid sheet 12 made of glass, and the light guide optic ismade of a polymer such as PMMA, it may only be necessary to provide acell envelope 21 about the photovoltaic cell 24 on the side facing thelight guide optic 40. The cell envelope 21 can be a dome (e.g., ahemisphere) of thermally insulating material, e.g., a polymer such assilicone or glass. The light guide optic 40 can therefore include acavity 45 complementary in shape to the cell envelope 21 to house thecell envelope 21. Alternatively, the cell envelope 21 may be filled witha gas such as air contained by the cavity 45. An example of a cellenvelope 21 and cavity 45, to thermally insulate the light guide optic140 from heat generated at the photovoltaic cell 24, is shown in FIG. 9.

FIG. 10 is a cross sectional view of an optical unit 208 including afocusing optic 250 optically bonded to the second surface 16 of areceiver substrate assembly 10, and a light guide optic 240 opticallybonded to the first surface 14 of the receiver substrate assembly 10. Inthis embodiment, the focusing optic 250 is formed of a plurality oflenses adjacent to one another and has rotational symmetry about thecentral axis 44. The lenses 52 can therefore form concentric rings aboutthe central axis 44. Although FIG. 10 shows a focusing optic 250 withthree lenses 52 on either side of the central axis 44, greater or fewerlenses may be used depending on the dimensions of the optical unit 8 andthe materials used.

The light guide optic 240 is stepped and substantially wedge-shaped incross section, having a plurality of reflective surfaces 242 separatedby step surfaces 246. A reflective surface 242 is positioned near thefocus of each lens 52, such that substantially all of the sunlight 11impinging upon the surface 54 of a lens 52 is focused by the lens 52toward the reflective surface 242. The focused light 13 is transmittedthrough the light transmissive body 251 of the focusing optic 250,through the rigid sheet 12 and through the light transmissive body 241of the light guide optic 240 to the reflective surfaces 246. Where theconductor pattern 30 includes heat spreader portions (not shown) thelenses 52 focus the light 13 through the gaps 80 of the heat spreaderportions 70 a, 70 b, 90 a, 90 b. The focused light 13 may be reflectedby the reflective surfaces 242 by total internal reflection or, wherethe reflective surfaces 242 are mirror coated, by specular reflection.The reflected light 15 is transmitted in the light transmissive body 241of the light guide optic 240 towards a conditioning surface 243, whichmay be a parabolic section in cross section and which reflects thereflected light 15 towards the photovoltaic cell 24. The reflected light15 may be reflected by the conditioning surface 243 by total internalreflection, or where the conditioning surface 242 is mirror coated, byspecular reflection. The path of the concentrated light 17, which hasbeen reflected by the conditioning surface 243, is focused towards thefocus of the parabola but intercepted by the photovoltaic cell 24 whichconverts the concentrated light 17 into electricity.

In embodiments having multiple reflective surfaces 242, each reflectivesurface 242 may be identical to the others such that substantially allof the light in the optical unit 208 is generally transmitted in thesame direction toward the conditioning surface 243, i.e., the light maybe collimated as shown in FIG. 10. Alternatively, the reflectivesurfaces 242 may be different from one another, such that a reflectivesurface or a group of reflective surfaces reflect light in onedirection, and another reflective surface or another group of reflectivesurfaces reflect light in another direction or directions

As shown in FIGS. 11 and 12, an optical unit 308, 408 can include afocusing optic 250, a receiver substrate assembly 10, a low index film 9and a light guide optic 340, 440. The low index film 9 has a lower indexof refraction than the light transmissive body 341, 441. An example of alow index film material is a layer of a low index polymer orpolytetrafluoroethylene (Teflon), which can be deposited onto the firstsurface 14 of the rigid sheet 12. The focused light 13 is transmittedthrough the light transmissive body 251 of the focusing optic 250,through the rigid sheet 12, through the low index film 9 and through thelight transmissive body 341, 441 and onto the reflective surfaces 342 a,342 b, 342 c.

In this embodiment, the reflective surfaces 342 a intercept the focusedlight 13 and reflect it, such that the reflected light 15 a istransmitted through the light transmissive body 341,441 of the lightguide optic 340,440 towards the low index film 9. The reflected light 15a is then reflected a second time by the low index film 9 via totalinternal reflection (TIR) and is transmitted towards a conditioningsurface 343, 443. Reflective surfaces 324 b intercept the focused light13 and reflect it directly towards the conditioning surface 343, 442.The conditioning surface 343, 443 reflects the reflected light 15 a, 15b towards the photovoltaic cell 24 for harvesting electricity.Reflective surfaces 342 c reflect the focused light 13 directly towardsthe photovoltaic cell 24. In these embodiments, the reflective surfaces342 a-342 c are separated by step surfaces 346. FIG. 11 shows an opticalunit 308 wherein each reflective surface 342 a, 342 b, 342 c has adifferent profile in cross section. FIG. 12 shows an optical unit 308having a group of two reflective surfaces 342 a, a group of tworeflective surfaces 342 b and a reflective surface 342 c. In analternative embodiment similar to that of FIG. 12, any number ofreflective surfaces 342 a, 342 b, 342 c and corresponding lenses 52 maybe included.

FIG. 13 shows a cross section of an optical unit 508 in which the lightguide optic 540 includes a plurality of reflective surfaces 542 a-542 d,each reflective surface 542 a-542 d having a different profile in crosssection from the others, separated by a plurality of step surfaces 546a-546 c each step surface 546 a-546 c having a different profile incross section from the others. The light guide optic 540 also includestertiary reflector 547 with a secondary reflective surface 549. The gap527 between the low index film 9 and the tertiary reflector 547 can befilled with a gas such as air or any suitable light transmissivematerial having a lower refractive index than the light transmissivebody 541 of the light guide optic 540. The secondary reflective surfaces549 can be mirror coated or they can reflect light by TIR.

Reflective surfaces 542 a and 542 b intercept the focused light 13 andreflect it towards the low index film 9, which further reflects thereflected light 15 towards a secondary reflective surface 549. Thesecondary reflective surface 549 then reflects the reflected light 15towards a conditioning surface 543 which reflects the light towards thephotovoltaic cell 24. Reflective surfaces 542 c and 542 d intercept thefocused light 13 and reflect if towards the conditioning surface 543,which redirects the light towards the photovoltaic cell 24. Theconditioning surface 543 may reflect the reflected light 15 one or moretimes. The conditioning optic 543 can include a parabolic section incross section and other curved or flat portions in order to concentratelight towards the photovoltaic cell 24. The focusing optic 550 mayinclude dead space 53 in the vicinity of the central axis 44.

FIG. 14 is a cross sectional view of an optical unit 608 generallysimilar to that of FIG. 13. In this embodiment the light guide optic 640includes a plurality of reflective surfaces 642 a-642 d, each reflectivesurface 642 a-642 d having a different profile in cross section from theothers, separated by a plurality of step surfaces 646 a-646 c each stepsurface 646 a-646 c having a different profile in cross section from theothers. The step surfaces 646 a-636 c, unlike those described in earlierembodiments, are also reflective. Additionally, the light guide optic640 includes a plurality of tertiary reflectors 647 with secondaryreflective surfaces 649, opposite the step surfaces 646 a-646 c. Forevery reflective surface 642 a-642 c, excluding the reflective surfaces643 d nearest the central axis, there is a corresponding secondaryreflective surface 649.

In this embodiment, light 11 impinging on the lenses 52 is focused bythe lenses. The focused light 13 is transmitted through the lighttransmissive body 551 of the focusing optic 550, through the rigid sheet12 and through the light transmissive body 641 of the light guide optic640 onto a reflective surface 642 a-642 d. Although the reflectivesurfaces 642 a-642 c and the step surfaces 646 a-646 c need not beidentical in shape, the trajectory of the light between them is similar:The focused light 13 is reflected by a reflective surface 642 a-642 ctowards a corresponding step surface 646 a-646 c. The reflected light 15is then reflected a second time by a step surface 646 a-646 c towards acorresponding secondary reflective surface 649 which reflects the lighta third time towards a conditioning surface 643, which further reflectsthe light towards the photovoltaic cell 24.

FIG. 15 shows a cross section of an optical unit 708 having a focusingoptic 250, a receiver substrate assembly 10, a redirecting optic 755, alow index film 709, and a light guide optic 740. The redirecting optic755 can be made of light transmissive materials including glass,polymeric materials such as injection molded poly(methyl methacrylate)(PMMA), polymethyl methacrylimide (PMMI), polycarbonates, cyclo olefinpolymers (COP), cyclo olefin copolymers (COC), polytetrafluoroethylene(PTFE), or silicones. In this embodiment, the redirecting optic 755 isassembled onto the first surface 14 of the rigid sheet 12, the planarsurface 759 of the redirecting optic 755 being optically bonded thereto.The non-planar surface 758 of the redirecting optic 755 includes aplurality of redirecting elements 756 with redirecting surfaces 757, andis coated by a low index film 709, such that the focused light 13 isreflected by a redirecting surface 757 via TIR. Alternatively, theredirecting surfaces 757 may be coated with a reflective material, whichmay be more economical than coating the entire non-planar surface 758with a low index film 709.

The light guide optic 740 includes a plurality of indentations 770shaped to house the redirecting elements 756. The light guide optic 740can be assembled onto and optically bonded to the redirecting optic 755using optical adhesive such as silicone. The light guide optic furtherincludes a reflective surface 742 that is continuous with a conditioningsurface 743. Light 11 impinging on the surface 54 of the lenses 52 isfocused and transmitted through the light transmissive body 251 of thefocusing optic 250, through the rigid sheet 12, and into the redirectingoptic 755, where the light is reflected by a redirecting surface 757.The reflected light 15 is transmitted out of the redirecting opticthrough output faces 771 adjacent to the redirecting surfaces 757, andinto the light guide optic 740 through input faces 772, which are partof the indentations 770. In the light guide optic 740, the reflectedlight can be reflected by the reflective surface 742 directly to thephotovoltaic cell, or to the conditioning surface 743. Light impingingon the conditioning surface 743 is concentrated towards the photovoltaiccell 24.

FIG. 16 shows a cross section of an embodiment of an optical unit 808 inwhich the path of light is generally similar to that of FIG. 15.However, in this embodiment, the light guide optic 840 is made with aplurality of tertiary reflectors 870 including redirecting surfaces 857.When the light guide optic 840 is assembled onto the first surface 14,air fills the gap 873 between the first surface 14 and the tertiaryreflector 870. In an alternative embodiment, the gap 873 can be filledwith any suitable material having a refractive index lower than that ofthe light transmissive body 841.

In this embodiment the focused light 13 converges towards the focalpoint of the lens 52, but before reaching the focal point, it isintercepted by a redirecting surface 857 the reflects the focused light13 by TIR. The reflective surface 842 is continuous with theconditioning surface 843. As in FIG. 15 the reflected light can bereflected by the reflective surface 842 directly to the photovoltaiccell, or to the conditioning surface 843. Light impinging on theconditioning surface 843 is concentrated towards the photovoltaic cell24.

FIG. 17 shows a cross section of an optical unit 908 in which the lightguide optic 940 includes a plurality of lenses 952 and reflectivesurfaces 942, and is attached to the rigid sheet 12 by means of opticalattachment features 974. The optical attachment features can beoptically and mechanically bonded, by means of an optical adhesive, tothe first surface 14 of the rigid sheet 12. Likewise, the cell envelope21, which in this embodiment must be made of a solid, opticallytransmissive material such as silicone, is mechanically and opticallybonded to a cavity 945 in the light guide optic 940.

Light 11 impinging on the second surface 16 of the rigid sheet 12, istransmitted to the light guide optic 940 through the optical attachmentfeatures 974 or through the lenses 952. Light 11 entering the lightguide optic through the lenses 952 is transmitted from the first surface14 of the rigid sheet 12 to a layer 975, which in some embodiments maybe air or any suitable light transmissive material. From the layer 975,the light 11 is transmitted to the lenses 952 which focus the lighttowards reflective surfaces 942, which reflect the light towards aconditioning surface 943. Light 11 entering the light guide optic 940through the optical attachment features 974 is transmitted directly fromthe first surface 14 of the rigid sheet to the optical attachmentfeatures 974. These optical attachment features 974 include reflectingsurfaces 976 which reflect the light impinging thereon towards theconditioning surface 943. Light impinging on the conditioning surface943 is then reflected towards the photovoltaic cell 24. The lenses 952are largest near the central axis 44 and smallest near the peripheraledge 980 of the optical unit 908. This is to adjust the focal lengths ofthe lenses 952 so that the overall thickness of the light guide optic940 may be reduced.

FIG. 18 shows a cross section of an optical unit 1008 having a paraboliclight guide optic 1040 optically bonded to the second surface 16 of areceiver substrate assembly 10. In this embodiment, light 11 typicallyimpinges on the rigid sheet 12 at an angle normal to the first surface14. The light 11 is transmitted through the rigid sheet 12, exitingthrough the first surface 14 into the light guide optic 1040. Thereflective surface 1042, which is a parabolic section in cross section,has a mirror coating 148 to reflect the light impinging thereon towardsthe focus of the parabola. The reflected light is transmitted throughthe light transmissive body 1041 of the light guide optic 1040 and backthrough the rigid sheet into a secondary optic 1077. The secondary opticincludes a mirror coated hyperbolic surface 1078, which intercepts thelight 15 before reaching the focus of the parabola. The hyperbolicsurface 1078 redirects the light towards the photovoltaic cell 24. Inthis embodiment, the conductor pattern 30 and cell receiver assemblies20 are assembled onto the first surface 14 of the rigid sheet 12.

FIG. 19 is a cross sectional view of an optical unit 1108 having thelight guide optic 1140 assembled onto the second surface 16 of the rigidsheet 12 and the conductor pattern 30 and the receiver assembly 20 onthe first surface 14 of the rigid sheet 12. In this embodiment thefocusing optic 1150 includes a secondary reflector surface 1178 and acavity 1179 for housing the cell envelope 21, which in this embodimentextends from the first surface 14 of the rigid sheet 12, covering thephotovoltaic cell 24 and the receiver assembly 20.

Light 11 impinging on the surface 54 of the lenses 52, is focused andtransmitted through the light transmissive body 1151 of the focusingoptic 1150, through the rigid sheet 12 and through the lighttransmissive body 1141 of the light guide optic 1140. Before the focusedlight 13 reaches the focus of the lens 52, it is intercepted by areflective surface 1142 which reflects the light towards a conditioningsurface 1143. The conditioning surface 1143 reflects the light backthrough the rigid sheet 12 and the light transmissive body 1151 of thefocusing optic 1150 to the secondary reflector surface 1178 whichfocuses the concentrated light 17 onto the photovoltaic cell 24.Reflections on the secondary reflector surface 1178 may be TIR orspecular reflections off a mirror coating applied to the secondaryreflector surface 1178.

FIG. 20 shows a cross section of an optical unit 1208 generally similarto the embodiment of FIG. 15 in that it includes a focusing optic 250, areceiver substrate assembly 10, a redirecting optic 755, and a lightguide optic 1240.

The light guide optic 1240 includes a planar reflective surface 1242, aplurality of step reflector surfaces 1281 opposite to the planarreflective surface 1242 and a conditioning surface 1243. The stepreflector surfaces 1281 are separated by input surfaces 1282 which aregenerally perpendicular to the step reflector surfaces 1281.

Light 11 is focused by the lenses 52 and then reflected by theredirecting surfaces 757. The light 15 reflected by the redirectingsurface 757 exits the redirecting elements 756 through the outputsurfaces 771, and enters the light guide optic 1240 through the inputsurfaces 1282. The reflected light is then transmitted in the lightguide optic 1240 by total internal reflections on the planar reflectivesurface 1242 and on the plurality of step reflector surfaces 1281 untilit reaches the conditioning surface 1243 which reflects the lighttowards the photovoltaic cell 24, There is an area 1275 between theredirecting optic 755 and the light guide optic 1240 that can be filledwith air or any suitable light transmissive material such as an opticaladhesive.

FIG. 21 is a cross section of an optical unit 1308 in which the lightguide optic 1340 includes focusing portions 1383 and guiding portions1384. The focusing portions 1383 include a plurality of reflectingsurfaces 1342 to reflect the light 11 into the guiding portions 1384.The light guide optic 1340 has a plurality of reflector elements 1385that can be filled with air or a light transmissive material having alower index of refraction than the light guide optic 1340, to allow TIRon the reflective surfaces 1342 and on a plurality of step reflectorsurfaces 1381.

In this embodiment, light 11 enters the optical unit 1308 through thesecond surface 16 and is transmitted to the plurality of reflectingsurfaces 1342 which reflect the light through an output area 1386 to aguiding portion 1384. The light in the guiding portions 1384 istransmitted via total internal reflections on the step reflectorsurfaces 1381 and on planar reflectors 1387 positioned opposite to thestep reflector surfaces 1381. The guiding portions 1384 guide the lighttowards a conditioning surface 1343 which focuses the light onto thephotovoltaic cell 24. Although, FIG. 21 shows a light guide optic 1340with two guiding portions 1384 and two focusing portions 1383, it ispossible to manufacture an optical unit with any number of focusingportions and corresponding guiding portions.

Turning to FIG. 22 there is provided an optical unit having a lightguide optic 1440 composed of three light guide stages 1440 a, 1440 b,1440 c. The first light guide stage 1440 a includes reflecting surfaces1442 a and a first conditioning surface 1443 a; the second light guidestage 1440 b includes reflecting surfaces 1442 b; and the third lightguide stage 1440 c includes a reflecting surface 1442 c and a secondconditioning surface 1443 c. The three light guide stages 1440 a, 1440b, 1440 c can manufactured separately, for example, by injectionmolding, 3D printing or embossing, and subsequently assembled together.The first and second light guide stages 1440 a and 1440 b are opticallybonded, for example, by means of an optical bonding agent at the bondinginterface surface 1489 denoted by the dotted line. Further, all threelight guide stages 1440 a, 1440 b, 1440 c can be bonded to the firstsurface 14 of the rigid sheet 12 by means of an optical bonding agent1488 b, for example a polymer such as silicone rubber or gel. As shownin FIG. 22, when the light guide optic 1440 is assembled, gaps 1490remain between the light guide stages 1440 a, 1440 b, 1440 c. These gaps1490 allow for TIR on the reflecting surfaces 1442 a, 1442 b, 1442 c andon the conditioning surfaces 1443 a, 1443 c.

A focusing optic 550 is optically and mechanically bonded to the secondsurface 16 of a rigid sheet 12 also by means of an optical bonding agent1488 a, for example a polymer such as silicone rubber or gel. Light 11impinging on the lenses 52 are focused towards the reflecting surfacesthe 1442 a, 1442 b and 1442 c. The reflecting surfaces 1442 a and 1442 bof the first and second light guide stages 1440 a, 1440 b reflect thelight towards the first conditioning surface 1443 a. Light travels fromthe second light guide stage 1440 b to the first light guide stage 1440a through the bonding interface 1489. The first conditioning surface1443 a reflects the light towards the photovoltaic cell 24. Thereflecting surface 1442 c of the third light guide stage 1440 c reflectslight towards the second conditioning surface 1443 c, which reflects thelight towards the photovoltaic cell 24.

FIG. 23 shows a cross section of an optical unit 1508 in which thefocusing optic 1550 includes a plurality of lenses 1552 and a pluralityof redirecting surfaces 1592. In this embodiment the light guide optic1540 has reflecting surface 1542 coated with a mirror coating 148. Lightimpinging on the lenses 1552 is focused towards the redirecting surfaces1592 which reflect the light through the rigid sheet 12 into the lightguide optic 1540. In the light guide optic 1540, the light 1542 istransmitted towards the reflecting surface 1542, which reflects thelight towards the photovoltaic cell 24.

As described in FIGS. 7A and 7B, conductor patterns employing heatspreader portions 70 may be electrically and thermally connected to theinterconnection traces 32 of an optical unit 8 in order to cool largeroptical units 8. FIG. 24A shows a cross section of an optical unit 1708employing conductor patterns such as those described in FIGS. 7A and 7B.This figure illustrates how the path of the focused light 13 is notinterrupted by the positive arms 76 or negative arms 78 of the heatspreader portion 70 a, and instead, the light 13 is transmitted throughthe gaps 80, into the light guide optic 1740.

The optical unit 1708 shown in FIG. 24A includes a focusing optic 1750,two layers of an optical bonding agent 1788 a, 1788 b, a receiversubstrate assembly 1710, and a light guide optic 1740. The focusingoptic 1750 is optically and mechanically bonded to the second surface 16of the rigid sheet 12 by means of an optical bonding agent 1788 a. Thelight guide optic 1740 includes a redirecting portion 1740 a and aguiding portion 1740 b which can be manufactured separately, for exampleby injection molding or embossing, and then assembled together by meansof an optical adhesive or any suitable optical bonding means. Whenassembled together, gaps 1790 remain between the redirecting portion1740 a and the guiding portion 1740, to enable TIR at a plurality ofreflective surfaces 1742 of the redirecting portion 1740 a.

As will be appreciated by those skilled in the art, optics of any of theoptical units described above can be employed as an illumination deviceby reversing the direction of light travelling therethrough andreplacing the photovoltaic cell 24 with a light source 25, such as alight-emitting diode (LED) or an organic light-emitting diode (OLED), aplasma light bulb, fluorescent light bulbs, or any other type ofsuitable light-source. In some embodiments the light source 25 can be anoptical fibre transferring light from source remote originating source(not shown). In order to illustrate this duality of the optical units,the direction of light rays 11 of FIGS. 24A-26 are omitted in order toshow that the light could be entering the optical unit through thelenses 1752, or it could be emerging therefrom. The heat produced by thephotovoltaic cell 24 or light source 25 is transmitted away from thecentral axis 44 towards the edges by means of the positive arms 76 andthe negative arms 78. The direction of heat transfer is shown in FIG.24B by arrows 1794.

In this embodiment, the receiver assembly 20 is coated with an opticaland dielectric encapsulant 1793, which in some embodiments may be thesame material as the optical bonding agent 1788 b. The envelope 1721thermally insulates the photovoltaic cell 24 or the light source 25 fromthe light guide optic 1740. The envelope 1221 can be a separate moldedcomponent. However, in one alternative embodiment, the optical bondingagents 1788 b, the encapsulant 1793 and the envelope 1721 can all bemade of the same material, for example silicone, and therefore theywould be a single component.

It is possible to assemble the light guide optic 1740 with the envelope1721 into a single solid piece by attaching the envelope 1721 to acavity 1745 in the light guide optic 1740. The redirecting portion 1740a, the guiding portion 1740 b and the envelope can be manufacturedseparately, for example by injection molding, and subsequently bondedtogether by means of a suitable bonding agent before being assembledonto the first surface 14 of the receiver substrate assembly 1710 bymeans of the optical bonding agent 1855 b. FIG. 24C shows how theredirecting portion 1740 a, the guiding portion 1740 b and the envelope1721 fit together.

An optical unit 1708 such as the one shown in FIGS. 24A-24C can behaveas a solar concentrator by focusing light 11 impinging on the surface1754 of the lenses 1752. The focussed light 13 is transmitted throughthe light transmissive body 1751 of the focusing optic 1740, the opticalbonding agents 1788 a, 1788 b, the rigid sheet 12 and through the gaps80 of the heat spreader portion 70 a of the conductor pattern 30 intothe redirecting portion 1740 a of the light guide optic 1740. Thefocussed light 13 is intercepted by a reflective surface 1742, whichreflects the light through the bonding interface 1789 into the guidingportion 1740 b where the light is reflected towards the photovoltaiccell 24 by a conditioning surface 1743.

The same optical unit 1708 of FIGS. 24A-24C can be used as anillumination device in the following manner. Light 17 diverging awayfrom the light source 25 is transmitted through the encapsulant 1793 andthe envelope 1721 into the guiding portion 1740 b of the light guideoptic 1740. The conditioning surface 1743 then reflects the lightthrough the bonding interfaces 1789 into the redirecting portion 1740 aof the light guide optic 1740 where the reflective surfaces 1742 reflectthe light such that it diverges away from the reflective surfaces 1742towards the lenses 1752. The light 13 diverges away from the reflectivesurfaces 1742 to the lenses 52 through gaps 80 in the heat spreader 70 aof the portion of the conductor pattern, thereby avoiding the positiveand negative arms 76, 78 and the positive and negative termini 72, 74.The lenses 1752 collimate the output light 11.

FIG. 25 show a cross section of an optical unit 1808 generally similarto the embodiment shown in FIGS. 24A-24C and any elements not describedin relation to this embodiment below can be found in the description ofthe embodiment above. The embodiment of FIG. 25 differs from that ofFIGS. 24A-24C only in that the envelope 1821 includes a spherical optic1895 and an encapsulating material 1896. The spherical optic 1895 can bea bead made of a light transmissive material capable of withstanding ahigh flux of light, such as glass or silicone. The encapsulatingmaterial can be air or any suitable light transmissive material. In someembodiments the encapsulating material may be the same material as thebonding agent 1788 b.

It is also possible to use the rigid sheet 12 for the same purpose as anenvelope 21, where the rigid sheet is made of a thermally insulatingmaterial such as glass. This can be achieved by positioning thephotovoltaic cell 24 or the light source 25 against the second surface16 with an encapsulant 1993 between the glass and the receiver assembly20. This encapsulant 1993 may extend to the edges of the optical unit1908 encapsulating the positive and negative arms 96,98 and forming anoptical bond between the focusing optic 1750 and the receiver substrateassembly 1910. In this embodiment, the positive terminus 1972 is raisedaway from the positive and negative arms 76, 78, and therefore, thefocusing optic 1950 has a groove 1994 to house the positive terminus1972. The positive terminus 1972 has extensions 1995 that extend to theglass in order to transfer heat thereto.

It will be appreciated by those skilled in the art that the photovoltaiccells 24 described above can be replaced by any suitable solar energycollector.

FIG. 27 is an isometric view of an assembled optical unit 1608 includinga light guide optic 1640, a receiver substrate assembly 10 and afocusing optic 1650. The rigid sheet 12 is cropped into a hexagonalshape for the purpose of illustrating a single assembled optical unit,however a CPV 2, as shown in FIG. 2, panel may include several opticalunits on a single rectangular receiver substrate assembly. Although thisembodiment shows a circular light guide optic 1640 and a circularfocusing optic 1650, these can be cropped into a tillable shape such asa square or a hexagon to eliminate dead space.

Modifications and improvements to the above-described embodiments of thepresent technology may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present technology is therefore intended to be limitedsolely by the scope of the appended claims.

1. A device for concentrating and harvesting sunlight comprising: apanel having at least one rigid layer, the at least one rigid layerhaving at least one patterned electrical circuit thereon; an array ofsunlight concentrating and harvesting units, each unit being formed byat least one rigid element and a portion of the at least one rigidlayer, each unit including: a rigid optical concentrating elementsecured to the at least one rigid layer for concentrating sunlightreceived by the unit, a photovoltaic cell secured to the at least onerigid layer and sandwiched within the panel for converting concentratedsunlight into electrical energy, and an electrical conductor inelectrical communication with the photovoltaic cell to receiveelectrical energy therefrom, the electrical conductor being in thermalcommunication with the photovoltaic cell to receive thermal energytherefrom, the electrical conductor being the primary heat sink for thephotovoltaic cell, the photovoltaic cell being primarily cooled viaconduction; the electrical conductor and the optical concentratingelement of each unit being dimensioned and arranged within the unit suchthat the electrical conductor does not materially impede transmission ofsunlight received by the unit within the unit to the photovoltaic cell;the electrical conductor being at least electrically and thermallyinterconnected with the patterned circuit to transmit electrical energyand thermal energy received from the photovoltaic cell away from theunit.
 2. The device of claim 1, wherein the photovoltaic cell issandwiched between the at least one rigid layer and the rigid opticalconcentrating element.
 3. The device of claim 1, wherein the opticalconcentrating element of each unit is a series of optical concentratingelements.
 4. The device of claim 3, wherein the optical concentratingelement of each unit is a series of concentric annular opticalconcentrating elements.
 5. The device of claim 1, wherein the rigidoptical concentrating elements of multiple units are all part of asingle rigid layer distinct from the at least one rigid layer having theat least one patterned electrical circuit thereon.
 6. The device ofclaim 1, wherein the electrical conductor and the optical concentratingelement of each unit being dimensioned and arranged within the unit suchthat the electrical conductor impedes transmission of no more than 20%of sunlight received by the unit within the unit to the photovoltaiccell.
 7. The device of claim 1, wherein each unit of the array furtherincludes a rigid optical redirecting element secured to the at least onerigid layer for redirecting sunlight received by the unit; and theelectrical conductor, the optical concentrating element, and the opticalredirecting element of each unit are dimensioned and arranged within theunit such that the electrical conductor does not materially impedetransmission of sunlight received by the unit within the unit to thephotovoltaic cell.
 8. The device of claim 7, wherein the photovoltaiccell is sandwiched between the at least one rigid layer and the rigidoptical concentrating element.
 9. The device of claim 7, wherein thephotovoltaic cell is sandwiched between the at least one rigid layer andthe rigid optical redirecting element.
 10. The device of claim 7,wherein the optical redirecting element of each unit is a series ofoptical redirecting elements.
 11. The device of claim 7, wherein theoptical concentrating element of each unit is a series of opticalconcentrating elements; and the optical redirecting element of each unitis a series of optical redirecting elements.
 12. The device of claim 7,wherein the optical concentrating element of each unit is a series ofconcentric annular optical concentrating elements; and the opticalredirecting element of each unit is a series of concentric annularoptical redirecting elements.
 13. The device of claim 7, wherein therigid optical concentrating elements of multiple units are all part of afirst single rigid layer distinct from the at least one rigid layerhaving the at least one patterned electrical circuit thereon; and therigid optical redirecting elements of multiple units are all part of asecond single rigid layer distinct from the at least one rigid layerhaving the at least one patterned electrical circuit thereon and thefirst single rigid layer.
 14. The device of claim 7, wherein the rigidoptical redirecting element redirects light into a light guide fortransmission to the photovoltaic cell.
 15. The device of claim 14,wherein the light guide has a secondary optical element for redirectinglight in the light guide.
 16. The device of claim 7, wherein theelectrical conductor, the optical concentrating element, and the opticalredirecting element of each unit are dimensioned and arranged within theunit such that the electrical conductor impedes transmission of not morethan 20% of sunlight received by the unit within the unit to thephotovoltaic cell.
 17. The device of claim 1, wherein the photovoltaiccell is at least partially encased in a thermal insulator.
 18. A devicefor concentrating and harvesting sunlight comprising: a panel having aplurality of rigid layers bonded together; an array of sunlightconcentrating and harvesting units formed by the plurality of layers ofthe panel, each one of the array of sunlight concentrating andharvesting units including: a series of optical concentrating elementsassociated with a first surface of one of the layers of the plurality oflayers for concentrating sunlight received by the unit; a series ofoptical redirecting elements associated with a second surface of one ofthe layers of the plurality of layers for redirecting sunlight receivedby the unit; a photovoltaic cell sandwiched between two of the layers ofthe plurality of layers for converting concentrated and redirectedsunlight into electrical energy; one of the layers of the plurality oflayers having an electrical conductor in electrical communication withthe photovoltaic cell to receive electrical energy therefrom, theelectrical conductor being in thermal communication with thephotovoltaic cell to receive thermal energy therefrom, the electricalconductor being the primary heat sink for the photovoltaic cell, thephotovoltaic cell being primarily cooled via conduction; the electricalconductor, the series of optical concentrating elements and the seriesof optical redirecting elements being dimensioned and arranged withinthe unit such that the electrical conductor does not materially impedetransmission of sunlight received by the unit within the unit to thephotovoltaic cell; one of the layers of the plurality of layers having apatterned circuit electrically and thermally interconnected withphotovoltaic cells of at least some of the units to receive electricalenergy and thermal energy therefrom for transmission away from theunits.
 19. The device of claim 18, wherein the series of opticalconcentrating elements are formed on the first surface; and the seriesof optical redirecting elements are formed on the second surface. 20.The device of claim 18, wherein the electrical conductor, the opticalconcentrating element, and the optical redirecting element of each unitare dimensioned and arranged within the unit such that the electricalconductor impedes transmission of not more than 20% of sunlight receivedby the unit within the unit to the photovoltaic cell.